The invention relates to a rotating anode x-ray tube wherein the anode shaft is supported by ball bearings which contain a lubricant, and a cover is provided for the purpose of keeping the lubricant in the bearing. Rotating anodes of this type are, for example, known from the British Patent No. 1,247,316.
In the known x-ray tubes great demands are made of the bearings because they run in high vacuum under temperature variation stresses. Therefore, in the case of bearings which must run in this manner for a long period of time without relubrication, in the construction known according to the abovecited reference, friction surfaces of a material capable of being lubricated have been manufactured. However, the danger here is that the lubricant forms a rubbed (or worn)-off residue which falls out of the bearing. Other lubricants introduced in the bearing in a known fashion, such as molybdenum sulfide and silver, etc., can likewise escape from the bearing causing an impairment of the lubrication of the latter.
In an x-ray tube according to the U.S. Pat. No. 2,280,886, in an embodiment, the ball bearings are provided with sealing parts which have the purpose of providing chambers for accommodating molybdenum sulfide as lubricant. However, bearings of this type with an encased (enclosed) ball race (or running) space have not proven successful in x-ray technology because, due to the large radial clearance necessary in order to absorb the temperature expansion, a gap must remain which is so wide that lubricant particles can escape and enter the tube-space.
Another x-ray tube, known according to the U.S. Pat. No. 2,570,770, has a bearing in proximity of the anode to which there is pre- (or series-) connected, on the side facing the plate, a receptacle with soft material as lubricant. The receptacle is to be mounted on the shaft. However, such a design has not proven successful because in the case of x-ray tubes the disadvantage arises that the receptacle co-rotates and lubricant particles can be spun (or centrifuged) into the tube space.